dump: qmp_dump_guest_memory(): use error_setg_file_open()

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Acked-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/dump.c b/dump.c
index 44a1339..c812cfa 100644
--- a/dump.c
+++ b/dump.c
@@ -853,7 +853,7 @@
     if  (strstart(file, "file:", &p)) {
         fd = qemu_open(p, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY, S_IRUSR);
         if (fd < 0) {
-            error_set(errp, QERR_OPEN_FILE_FAILED, p);
+            error_setg_file_open(errp, errno, p);
             return;
         }
     }